Heat exchanger and a manifold for use therein

ABSTRACT

A heat exchanger includes a manifold and a tube array. The manifold has an internal void and walls that surround the void and merge one with the other via corners. Each wall has a middle portion that is located mid way between the corners merging with the wall and the manifold branches off to attach and communicate with the tube array at a location aside of the middle portion of one of the walls towards a corner that merges with the wall.

TECHNICAL FIELD

Embodiments of the present invention relate to a heat exchanger forheating a liquid medium and to a manifold of the heat exchanger thatdistributes and/or gathers the liquid medium.

BACKGROUND

In such a heat exchanger, liquid such as water may be distributed viathe manifold into an array of plastic tubes. The water flowing in thetubes, when exposed to heat such as solar radiation, may absorb the heatand then flow onwards to be utilized.

U.S. Pat. No. 7,112,297 describes a device that may be used as a solarcollector that includes a plurality of hollow conduits joined betweenhollow manifolds. The manifold which preferably has a circularcross-section may include a subplenum adaptor that serves as adistribution chamber for uniformly distributing water to the tubes.

SUMMARY

The following embodiment and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope.

In an embodiment of the present invention there is provided a heatexchanger that comprises a manifold and a tube array, the manifoldextends along an axis X between two ends and comprises an internal voidand axially extending walls that surround the void, each given wallmerging with an adjacent wall via an axially extending corner andcomprising an axially extending middle portion that is located mid waybetween the corners merging with the given wall, the manifold branchingoff to attach and communicate with the tube array, wherein the branchingoff of the manifold forms a one piece unitary construction with themanifold and occurs at a location parallel to the middle portion of agiven one of the walls and on the given wall towards a given one of thecorners that merges with the given wall.

Optionally, the branching off of the manifold occurs at least partiallywhere the given wall merges with the given corner.

Typically, the walls of the manifold are adapted to at least partiallyflex above a threshold pressure in the manifold, and the given wallmerging with the given corner is adapted to flex less than the otherremaining walls.

Optionally, in a cross section perpendicular to the axis taken throughthe manifold the walls reside on an outline of a polygon.

If desired, the polygon is a rectangle.

Optionally, the heat exchanger may be used in a housing being of closedbox-like shape and constituted by an assembly of a receiving member andan at least partially transparent cover member, the tube array beinglocated in the housing so that solar radiation passing through the coveris at least partially absorbed by the tube array to heat the liquid inthe tube array.

Typically, each corner of the manifold except for the given corner issubstantiality free of any reinforcing structure that projects out ofthe corner and extends axially therealong between the two ends of themanifold.

Optionally, the branching off of the manifold occurs only at onelocation on the manifold on the given wall thereby leaving the remaininglocations on the given wall and the remaining walls of the manifoldsubstantially free to flex and absorb distortion due to rise of internalpressure in the manifold above a threshold pressure.

Typically, the heat exchanger comprises a plurality of through goingholes formed in the manifold where it branches off and the tube arraycomprises a plurality of tubes, wherein said holes provide liquidcommunication between the void of the manifold and the tubes of the tubearray.

Optionally, at least one enclosed chamber is formed in the heatexchanger where the manifold and tube array attach, said chambercommunicating with at least part of the holes and with at least part ofthe tubes.

If desired, a first part of the chamber is formed in the manifold and asecond part of the chamber is formed in the tube array.

Optionally, a total cross sectional area of the holes that open into thechamber is smaller than a total cross sectional area of the tubes thatopen into the chamber.

Optionally, each given hole perpendicularly opens into the chamber at aface and in a plane perpendicular to the axis X and passing through acenter of a given hole an imaginary cylindrical surface extendingco-axially with the given hole has a diameter equal to a width of theface as measured in that plane, the given hole has a diameter DH and aneffective wall thickness TH measured between its periphery and thecylindrical surface surrounding it, the void has an effective diameterDM that is the distance that opposing walls of the manifold are spacedapart and a given wall of the manifold has an effective-wall thicknessTM, wherein a ratio of TH/DH is larger than a ratio of TM/DM.

Further optionally, in a plane perpendicular to the axis X and passingthrough a center of a given tube the given tube has a diameter DT and aneffective wall thickness TT that surrounds the given tube, an inner partof the chamber at a location where a given tube opens into the chamberhas an effective diameter DI as measured in the plane and a part of thetube array that is located above or below that location as measured inthe plane has an effective-wall thickness TI, wherein a ratio of TI/DIis larger than a ratio of TT/DT.

Even further optionally, in a plane perpendicular to the axis X andpassing through a center of a given tube the given tube has a diameterDT and an effective wall thickness TT that surrounds the given tube, thevoid has an effective diameter DM that is the distance that opposingwalls of the manifold are spaced apart and a given wall of the manifoldhas an effective-wall thickness TM, wherein a ratio of TM/DM is largerthan a ratio of TT/DT.

In an embodiment of the present invention there is also provided a heatexchanger comprising a manifold and a tube array, the manifold extendsalong an axis X between two ends and comprises an internal void andaxially extending walls that surround the void, each given wall mergingwith an adjacent wall via an axially extending corner and comprising anaxially extending middle portion that is located on the given wall midway between the corners merging with the given wall, the manifold beingadapted to flex under a rise of internal pressure in the manifold abovea threshold pressure with a maximum flex being adapted to occur at leastat middle portions of walls with no branching off structures, and themanifold branching off to attach and communicate with the tube array ata single location that is parallel to the middle portion of a given oneof the walls and on the given wall towards a given one of the cornersthat merges with the given wall.

Optionally, the branching off of the manifold forms a one piece unitaryconstruction with the manifold.

Typically, the branching off of the manifold occurs at least partiallywhere the given wall merges with the given corner.

In addition to the exemplary aspects and embodiment described above,further aspects and embodiments will become apparent by reference to thefigures and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE FIGURES

Exemplary embodiments are illustrated in referenced figures. It isintended that the embodiments and figures disclosed herein are to beconsidered illustrative, rather than restrictive. The invention,however, both as to organization and method of operation, together withobjects, features, and advantages thereof, may best be understood byreference to the following detailed description when read with theaccompanying figures, in which:

FIGS. 1 and 2 schematically show respectively a perspective view and anexploded perspective view of an optional use of a heat exchanger inaccordance with an embodiment of the present invention in a solarcollector;

FIG. 3 schematically shows a perspective view on an upper part of theheat exchanger incorporating three manifolds in accordance with anembodiment of the present invention attached each to a tube array;

FIG. 4 schematically shows a perspective view of one of the manifoldsattached to a tube array;

FIG. 5 schematically shows a perspective front view of the manifoldshowing a side of the manifold that branches off for attachment to atube array;

FIG. 6 schematically shows a perspective view of the tube array from aside that attaches to the manifold;

FIG. 7 schematically shows a perspective back view of the manifold;

FIG. 8 schematically shows a cross sectional view of the manifold;

FIG. 9 schematically shows a cross sectional view of the manifoldattached to the tube array; and

FIG. 10 schematically shows a cross sectional view of the manifoldattached to the tube array when subjected to a rise of pressure in theheat exchanger.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated within the figures toindicate like elements.

DETAILED DESCRIPTION

Attention is first drawn to FIGS. 1 and 2. A heat exchanger 10 inaccordance with an embodiment of the present invention is formed ofthree upper and three lower manifolds 12 and three tube arrays 14 thatextend therebetween. The heat exchanger 10 may optionally be used in asolar collecting system 16 that has a closed box like housing thatincludes a receiving member 18 and a transparent cover member 20 andsolar radiation passing through the cover member 20 may be absorbed bythe heat exchanger 10 to heat liquid flowing therein.

The manifolds 12 and tube arrays 14 of the heat exchanger 10 areoptionally made of plastics that are stabilized for outdoor usage suchas thermoplastic polypropylene copolymer and optionally said plasticshave a glass transition temperature that is below zero degrees Celsius.In embodiments of the present invention the heat exchanger 10 may beused in other types of systems and/or applications such as agriculturalroot zone heating, chemical heat exchanging systems, geothermal groundsource heat pumps, pond heat exchanging systems, ice storage heatexchanging systems, (etc.). It should be noted that directional termsappearing throughout the specification and claims, e.g. “forward”,“rear”, “up”, “down” etc., (and derivatives thereof) are forillustrative purposes only, and are not intended to limit the scope ofthe appended claims. In addition it is noted that the directional terms“down”, “below” and “lower” (and derivatives thereof) define identicaldirections.

Attention is now drawn to FIGS. 3 and 4. Each manifold 12 extends alongan axis X between two axial ends 22 and has an internal axiallyextending void 24 that opens out of the manifold 12 at the two ends 22.The void 24 is surrounded by four axially extending optionally planarwalls 26 of the manifold 12 and each wall 26 merges via an axiallyextending corner 28 with an adjacent wall 26 that extendsperpendicularly thereto. Each given wall 26 has an axially extendingmiddle portion 27 that is located mid way between the two corners 28that are located on both sides of the given wall 26 (middle portions 27are indicated in Fig, 8) and under internal pressure in the void 24 eachwall 26 that is free of any branching off and/or reinforcing structuresis adapted to flex most at its middle portion 27.

The manifold 12 optionally branches off to attach and form liquidcommunication with a tube array 14 of the heat exchanger 10 at alocation parallel to the middle portion 27 of a given one of the walls26 towards a given one of the corners 30 that merges with the given wall26. Optionally, that branching off of the manifold 12 occurs at alocation where the given one of the walls 26 merges with the given oneof the corners 28 of the manifold 12. Said branching off of the manifold12 forms a structure that is preferably integrally formed with themanifold 12 to form a one piece unitary construction with the manifold12 that reinforces the manifold 12 at a location where through goingliquid conducting passages that are formed through the manifold 12typically weaken the manifold 12.

In an embodiment of the present invention, the branching off of themanifold 12 at the merge with a given one of the corner 28 reinforcesthat corner 28 (hereinafter optionally referred to as “reinforcedcorner”) while the remaining other corners 28 of the manifold 12 areleft free of any reinforcing structures (hereinafter optionally referredto as “free corners”). In embodiments of the present invention the heatexchanger 10 may include a single tube array 14 extending between a pairof manifolds 12 or any given number of tube arrays 14 and correspondingpairs of manifolds 12 as required in the application in which the heatexchanger 10 is used. For example, in the embodiment shown in FIG. 1 theheat exchanger 10 includes three tube arrays 14 that extend betweenthree pairs of manifolds 12.

Attention is drawn to FIG. 5. A port 30 of the manifold 12 that projectsout of the manifold 12 where it branches off to attach and communicatewith the tube array 14 forms at least part of the reinforcement of thereinforced corner 28 by extending along that corner 28 between the twoaxial ends 22 of the manifold 12. The port 30 has a series of recesses32 formed at its outer side that is distal of the manifold 12. Eachrecess 32 has a floor 33 and a raised wall 35 that extends along aperimeter of the floor 33 and a portion of each wall 35 that is locatedbetween adjacent recesses 32 acts as a partition 34 between thoserecesses 32.

Attention is additionally drawn to FIGS. 7 and 8. An axially extendingoptional rib 36 of the manifold 12 extends along an inner side of thereinforced corner 28 within the void 24 between the two axial ends 22 ofthe manifold 12. The optional rib 36 acts as an additional optionalstructure that reinforces the reinforced corner 28 and a plurality ofthrough going liquid conducting passages or holes 38 extend through therib 36, port 30 and reinforced corner 28. Each hole 38 opens into thevoid 24 of the manifold 12 at the rib 36 and opens out of the manifold12 into a given one of the recesses 32 of the port 30 at the floor 33 ofthe given recess 32. As best seen in FIG. 5, each recess 32 acts as abasin into which several axially adjacent holes 38 collect.

Attention is drawn to FIG. 6. The tube array 14 has a plurality offlexible plastic tubes 40 that are attached at both ends to an innerside of an insert 42 of the tube array 14 and the insert 42 has a seriesof recesses 44 formed on its outer side with a series of partitions 46being spaced along the insert 42 between adjacent recesses 44.

Attention is now drawn to FIGS. 4 and 9. In the heat exchanger 10, themanifold 12 is attached at an outer face of its port 30 by optionallyheat bonding to an outer face of the insert 42 of the tube array 14.Each recess 32 in the port 30 of the manifold 12 meets in the heatexchanger 10 a corresponding recess 44 of the insert 42 to form anenclosed chamber 48 that is adapted to communicate via a group ofaxially adjacent holes 38 on the one hand with the void 24 of themanifold 12 and via a group of axially adjacent tubes 40 on the otherhand with the tube array 14.

Attention is specifically drawn to FIG. 9. In the manifold 12 thefollowing features may be defined in a cross section perpendicular tothe axis X that passes through a center of each given hole 38. Animaginary cylindrical surface C may be defined extending co-axiallyabout each given hole 38 with the diameter of the cylindrical surface Cbeing equal to a width K of the floor 33 as measured in the crosssection. An effective-wall thickness TH around each given hole 38 may bedefined between a periphery of the given hole 38 and the cylindricalsurface C that surrounds that given hole 38 and each given hole 38 maybe defined as having an internal diameter DH. The void 24 of themanifold 12 may be defined as having an effective-diameter DM that isthe distance that the inner faces of opposing walls 26 of the manifold12 are spaced apart and the walls 26 of the manifold 12 may be definedas having an effective-wall thickness TM.

In the tube array 14 the following features may also be defined in across section perpendicular to the axis X that may pass through a centerof each given tube 40. Each given tube 40 may be defined as having aninternal diameter DT and a wall thickness TT that surrounds the giventube 40 and an inner part of each recess 44 of the insert 42 at alocation where a given tube 40 opens into the recess 44 may be definedas having an effective diameter DI as measured in the cross section anda part of the insert 42 that is located above or below that location asmeasured in the cross section may be defined as an effective-wallthickness TI.

Optionally, a ratio of TH/DH may be larger than a ratio of TM/DM so thatthe manifold 12 may have a pressure rating at the holes 38 that ishigher than the void 24 and thereby may be designed to better withstandinternal pressures at the holes 38 in relation to the void 24.

Further optionally, a ratio of TI/DI may be larger than a ratio of TT/DTso that the tube array 14 may have a pressure rating at the insert 42that is higher than the tubes 40 and thereby may be designed to betterwithstand internal pressures at the insert 42 in relation to the tubes40.

Yet further optionally, a ratio of TM/DM may be larger than a ratio ofTT/DT so that the heat exchanger 10 may have a pressure rating at thevoid 24 that is higher than the tubes 40 and thereby may be designed tobetter withstand internal pressures at the void 24 in relation to thetubes 40.

The diameters DH of the holes 38 in the manifold 12 are optionallysmaller than the diameters DT of tubes 40 in the tube array 14 so thatthe total cross sectional area of the holes 38 is optionally smallerthan the total cross sectional area of the tubes 40. In some embodimentsof the present invention, the smaller cross sectional area of the holes38 may act to reduce the flow out of the manifold 12 thereby assistingto uniformly distribute liquid along the manifold 12.

Attention is now drawn to FIGS. 2 and 9. In different embodiments of theheat exchanger 10 various flow patterns may exist. For example in anembodiment of the heat exchanger 10, liquid flowing downstreamoptionally into the voids 24 of the upper manifolds 12 optionallybranches off out of the upper manifolds 12 via the holes 38 into thechambers 48 that are associated with the upper manifolds 12. From there,the liquid may flow downstream into the tubes 40 of the tube arrays 14where most of the heat exchange between the liquid located in the tubes40 and the environment outside of the tubes 40 is adapted to occur. Theliquid flowing downstream and out of the tube arrays 14 reaches thechambers 48 associated with the lower manifolds 12 and from there viathe holes 38 reaches the voids 24 of the lower manifolds 12 andoptionally flows out of the heat exchanger 10 for utilization.

During use, the heat exchanger 10 may be subjected to varying forcesthat are imposed thereupon by the liquid that is located therein. Theliquid in the heat exchanger 10 may reach for example a temperature ofabout 80 to 90 degrees Celsius and a pressure of about 6 to 7atmospheres when heated for example by solar radiation and on the otherhand may exhibit freezing during cold weather conditions. Liquid such aswater that may be used in a heat exchanger 10 may for example expand andform an increase in volume of about 9% when freezing under atmosphericpressure thereby imposing considerable forces upon the heat exchanger 10that may act to distort the heat exchanger 10.

Attention is now drawn to FIG. 10. In some embodiments of the presentinvention, an increase of pressure in the void 24 that is indicated inthis figure by small arrows 23 may act to distort the portions of themanifold 12 surrounding the void 24. In the heat exchanger 10 inaccordance with some embodiments of the present invention, thereinforced corner 28 of the manifold 12 is reinforced to such an extentthat the structured “handicap” that is formed therein by the throughgoing holes 38 which may weaken the ability of the corner 28 towithstand stress is strengthened and reinforced by the additionalreinforcing structures that are associated therewith.

The branching off structure of the port 30, the insert 42 structure ofthe tube array 14 that is bonded to the port 30, and the optional rib 36are examples of such structures that may be associated with thereinforced corner 28 and may each independently improve its ability towithstand stress and exhibit less distortion. As a result, underinternal pressure in the void 24, the portions of the manifold 12 moredistal of the reinforced corner 28 are adapted to flex and exhibitdistortion to a larger extent in relation to portions of the manifold 12more proximal to the reinforced corner 28. Optionally, the free corners28 of the manifold 12 are deliberately left free of any substantialreinforcing structures that extend axially therealong between the twoends 22 of the manifold 12 and project out of the corners 28 so thatthey may be free to absorb as much distortion as possible and therebylimit any stress that may be imposed upon the reinforced corner 28 dueto a rise in the internal pressure in the manifold 12.

In an embodiment, under internal pressure in the void 24 the given wall26 from which the branching off occurs or the two walls 26 merging viathe reinforced corner 28 is/are adapted to flex to a lesser extent andexhibit less distortion in relation to the remaining walls 26 of themanifold 12 that are more distal of the given wall 26 or reinforcedcorner 28.

In the description and claims of the present application, each of theverbs, “comprise” “include” and “have”, and conjugates thereof, are usedto indicate that the object or objects of the verb are not necessarily acomplete listing of members, components, elements or parts of thesubject or subjects of the verb.

Although the present embodiment has been described to a certain degreeof particularity, it should be understood that various alterations andmodifications could be made without departing from the scope of theinvention as hereinafter claimed.

1. A heat exchanger comprising: a manifold having: axially extendingwalls that enclose an internal void and are joined at axially extendingcorners; and a port extending along one of the corners that projects outfrom a wall of the plurality of walls and comprises a plurality ofrecesses, each recess surrounded by a raised wall and formed having atleast one through hole that connects the recess to the internal void;wherein the walls and port form a one piece unitary construction; and atube array attached to the port.
 2. The heat exchanger according toclaim 1 and comprising a plurality of reinforcing structures integrallyformed with the one piece unitary construction, each reinforcingstructure joining a portion of the raised wall of a recess with the wallfrom which the port projects.
 3. The heat exchanger according to claim 1and comprising an internal rib that extends along the corner along whichthe port extends.
 4. The heat exchanger according to claim 1 wherein theat least one through hole comprises a plurality of through holes.
 5. Theheat exchanger according to claim 1, wherein the walls of the manifoldare adapted to at least partially flex above a threshold pressure in themanifold, and wherein the wall from which the port extends is adapted toflex less than the other walls.
 6. The heat exchanger according to claim1 wherein the tube array comprises an insert having recesses thatcorrespond to the recesses of the port.
 7. The heat exchanger accordingto claim 6 wherein the insert is attached to the port.
 8. The heatexchanger according to claim 6 wherein the corresponding recesses of theport and insert form a plurality of enclosed chambers each of whichcommunicates with at least one of the through hole in the port and atleast one of the tubes in the tube array.
 9. The heat exchangeraccording to claim 8, wherein a total cross sectional area of the atleast one through hole that communicates with each of the plurality ofchambers is smaller than a total cross sectional area of the at leastone tube that communicates with the chamber.
 10. A manifold comprising:a plurality of axially extending walls that enclose an internal void andare joined at axially extending corners; and a port extending along oneof the corners that projects out from a wall of the plurality of wallsand comprises a plurality of recesses, each recess surrounded by araised wall and formed having at least one through hole that connectsthe recess to the internal void; wherein the walls and port are formedas a one piece unitary construction.